1. Field of the Invention
The invention refers to an expansion hose for the reduction of pressure pulsations in hydraulic systems.
Such expansion hoses are employed among others in power steering plants of automotive vehicles, in which the expansion hose reacts at varying operating pressures with a change of the volume of the hose by expansion and reduces therewith the pressure pulsations originating from the pump. This reduction of the pressure pulsations depends from the length, the cross-section and the volume expansion of the expansion hose. Because, however, it is not possible to arbitrarily select for instance in a vehicle the above mentioned values due to the limited space available for the mounting the desired reduction of the pressure pulsations is in many cases not sufficient.
2. Description of the Prior Art
In order to obtain better results it is already known to arrange in the outer expansion hose a further inner flexible hose which at the one end is connected to the inlet side end piece and ends freely with its other open end in the outer expansion hose. It is, furthermore, also known to forsee additionally a throttle member about at the center of the outer expansion hose and which divides the outer expansion hose into two hose chambers which communicate with each other through a throttle port whereby the inner hose comprises at the area of the first chamber located at the inlet side radial ports into the first hose chamber. The flow resistance in the inner hose shall, thereby, lead to a phase shift between the two hydraulic flows into the hose chambers at the inlet end and the outlet end wherewith a reduction of a pulsation and noise is obtained.
It has, however, now been found that this expenditure for a reaching the desired object is not at all necessary. Furthermore, there can be a problem at the known expansion hose in that the inner hose ends freely in the outer hose because it depends here from the material selected for the inner hose; if not a uncontrollable position of the two hoses relative to each other leads to a damaging at the inner side of the outer hose by which finally a defect of the expansion hose results for which the reason is not immediately recognizable.